The Deal (Used to be called Nightmare)
by aPieceOfPie
Summary: A few months after his arm was turned into a monster, it came back in full swing. Desperate to hide it and all the symptoms, Marco follows a letter saying it has medicine to fix the symptoms. This leads to him associating with a dangerous man. Will he be able to keep this from Star? "Never will he let it take over him. He'd rather become left handed then let it over take him."
1. Prologue

That thing inside him is there, he can feel it, hear it, and see it. Never will he let it take over him. He'd rather become left handed then let it over take him. He is very tempted to. But that would only put a huge guilt over Star. She knows nothing of the voice that hunts him some nights. She had so much guilt in her face and lost to much sleep when it first appeared. He couldn't let her take the blame. Yes, she did use her wand to try to heal his broken arm, but it was his fault for asking and implanting the seed of an idea in her head.

It was funny how things work out sometimes. He'll never brush off the saying, "Be careful what you wish for," again now that he learned the truth behind it. He has to decide to say something or just ignore and push all this down until he forgets about its presents, even for ten minutes.

Marco Diaz is no monster. No, he is, just part now. Fighting against the power he has, or should he say It has. Sitting on the bathroom floor in just pants, and having to hold his arm as it shoots pain that he probably deserved, it was so pathetic. He shouldn't have to take breaks in between activities just to calm the heated burning, painful spikes his right arm held. He should be able to just in the shower without a problem. But he has a problem.

Night is the time it really comes to bit his ass. It's night when the monsters like to crawl out. He's demons come to get him with that _thing_. All his negativity comes to the surface. It was a bitter time. He loved the night; the beauty of the unknown was something he always loved to think about. Now, the unknown just seemed like a place he shouldn't think about messing with. All he'd find is his problem and possibly gain some type of insanity. He wants, _needs_ , his sanity more than anything if he was going to get through this and help protect Star and her wand.

Sweat stuck to him like a leach. His body's way to try to calm and cool him off, reassurance that he couldn't accept. It just showed that he was too weak to handle this. He slowly got up, shaking, but he was able to this act. Though this only aggravated his arm causing a low growl to come up his throat. Marco made his was to the shower as fast as his body could allow. His mind was fuzzy and all he could hear was the _thing_ saying that he'd never get rid of him, never going to defeat him, and he should _**just give up trying to resist the power.**_

Marco slammed his right arm down on the cold water handle. The force knocked the handle loose and the pain became insufferable. He let out a scream that has been held back for so, so long. He knew it was a mistake. His parents were out, so Star would most likely hear the scream. He collapsed on his knees; hanging his head in shame.

The cold water ran down his back, washing his discomfort caused by the stickiness of the sweat. He really thought the coldness would cure all his discomfort, but the burn in his arm was still there. The burn isn't leaving him and he knows that. What foolish thoughts he had to even _think_ it would leave him. This 'virus' was apart of him, apart of his being.

He let a bitter smile come over his face. Yes, it was him, wasn't it? How blind can he be? Very blind, and even realizing this, he won't let it win. Even if it's apart of him, it will never take over him anytime soon. Choosing not to listen to the monster's screams of negativity and he focuses on the coldness and numbness he feels.

"M-Marco?" She sounds cautious.

He doesn't respond, tightening his grip on his right arm. His arm throbbed more, but he bit his tongue so no sound came out.

"Is everything okay? I heard you scream; was it a monster attack?" She asked with the words flying out in panic. Star glanced around the dark room, seeing no damage and frowned. Nothing seemed damaged.

"Marco?" She called out more quietly with hint of concern laced around it. Star started to move closer to her dear friend. He just sat there, soaked in cold water and on his knees. His bitter smile has completely left his face, and is replaced with a indifferent expression in an attempt to cover the conflict in his head and the growing, agonizing pulse in the arm.

"Y-yes?" Marco spat through clenched teeth. He slapped himself mentally. Star doesn't deserve to be spoken too like that.

 _ **Yes, you shouldn't have her; you never will deserve her! Just let me out and I'll make sure you will!**_

Marco let out a roar of fury and slammed his arm into the glass door of the shower; shattering the spot. That voice knows nothing! It will never get him to do anything that'll hurt others.

Star shrieked in horror and stepped back so quick that she fell on her butt. Never had she seen that much anger in Marco's eyes. It scared her too see that, but stopped thinking that she should stay away when another scream of anguish pierced the quiet air. She watched frozen in place as he held his arm close to his chest, ignoring the blood that came up at the surface cuts the glass gave him.

"You bastard," He cursed under his breath, keeping a gaze on his right arm.

 _He's not talking to you,_ Star thought to herself. He'd never say something like that, would he?

"I-I'm...Sorry," Marco says in between pants to keep his voice as even as possible.

She watches as he turns the water off with care, unlike when he had turned it on. He had gotten up and held the side bar in the shower with his left hand.

"Marco, what is going on?" She demanded. Star just couldn't accept that he was hiding something that seems so, so bad. He has been cheery and the same worrisome boy she met on her first day. What had changed?

"Nothing, Star," He replied as he staggered over to the sink counter. He took a wrap and started to wrap his arm not really caring if glass is stuck in his arm.

She gasped in disbelief, "Uh, no, there is no way you would scream and do any of that-that slamming if something wasn't up!"

"Heh," Marco let out a breath, "Maybe I just needed to let something out."

He was quite surprised that he could make a full sentence, but then again talking is taking his focus of the monster. The throbbing was there, but it calmed down. It normally does this; now he just has to wait for the next attack of the night. He shouldn't be able to be around her now. It's too dangerous.

"You let out your anger when we fight monsters!" She yelled in exasperation; her hands waving around.

Marco pulled sharply on the wrap, "And how do you know that?! What if I'm just doing that for you?"

"What?" Star took a step forward so she was right next to the boy. Seeing his arm full of bits of glass and how red it had gotten, like it was inflamed.

She gasped, "Marco! Your arm!"

She grabbed his arm and unwrapped it not noticing the hiss coming from the boy's clenched jaw. Star grabbed the bits of glass out of his few wounds, brushing off the rest that suck to his soaked arm. This was completely unbelievable. This so isn't her Marco, or isn't the Marco she's familiar with.

He let out a sigh, still holding in the growing burning throb that she was giving him, "Star, I'm fine. I do like fighting monsters; just not my own."

"Marco, you don't have any," Star said tiredly as she continued to work on his wounds. She added to much pressure, but he wasn't going to say a thing.

"How are you so sure?" He questioned with curiosity.

She stopped her movements and glanced up in question. Sure, he was almost possessed by a monster arm, but he's pretty healthy. She's seen his medical records and hasn't seen anything about a mental illness.

Marco pulls his arm back and holds it as it's getting more intense like earlier, "Look, this isn't your problem. You shouldn't worry about me. I'm sorry to make you worry."

"Why don't you tell me what's wrong?"

Marco ignores her question and looks around for a towel. She can't know; she'll find out anyway. It's safer for him to keep it from her. It will taunt him about her saying that he's a monster and if he can't gain control or even keep control, the _thing_ will hurt her.

Star grabs his left arm, then his face and forces him to look at her, "Don't you go walking away from me. Answer me!"

"NO!" He yelled. And there it is.

His arm tingled and ached. It all came back in full force. Marco crumbled to his knees once again and held on his right arm for dear life. Star was shocked at the sight of her brave, strong, and smart friend crumbling over pain in such an intense way. Then it clicked.

"Y-your arm..."

Marco sucked in a breath. He knew she knew now. The bastard in him made sure of it. Or it was possibly him? No, he tried, but that bastard was him too now. His face fell.

"Oh my gosh, Marco! I am so, so, so sorry!" She said as she fell next to him. Her eyes were filled with tears, "I can't believe I did this to you."

"It is _not_ your fault, Star," He says in gasps. Sweat started to appear again, but he was glad that the water on him masked it. Star would freak out more if she saw it.

"Yes, it is. Marco, I used my wand on you with out practice," Star says sadly, reaching out to hold his left hand.

Marco has always enjoyed her tiny ways of reassurance. Her touch gave a calming affect on him; it made him think of his mother's pat she gave him when ever he cried over simple mistakes.

"I pushed you to," He told her sternly.

Star paused, unsure of what to say. As much as she hated to admit it, he did ask. But she also agreed like an idiot. So, they both were at fault, no matter how much they disagree to that.

"We'll figure something out, Marco," Star smiles. She didn't fight over whose at fault because Marco would be too stubborn to say it was a joint effort.

"I-I want my arm chopped off," He said casually, well as casually as one could with a fuzzy mind.

"What?! No!" She shrieked and grabbed his right arm, "We are _not losing limbs_!"

Marco let out a strained chuckle, "Yeah, I know. How about a spell for pain? Earth medicine isn't cutting it."

Star slowly let his slightly pink arm go, and started thinking of a possible spell. She did see one in the book before, but she would need to dig to find it again. Glossaryck is on vacation so she'll have to do it herself. That or she'll have to ask her mother, but that could turn bad.

Marco smiled softly to himself when he saw her cute expression. Her eyebrows were scrunched together and her eyes stared off in the distance. With her lips in a small frown, it just made him feel better. But as soon as his happiness came, it was gone. The monster's voice in his head was not something he's going to tell her soon. With all this said, no mater how much agony, and torment he's being put through, Star will be with him. She has a way of making him ignore those horrible effects the being inside him gives.

It will be all right, as long as Star keeps him grounded. After all, if the monster wants her bowels, well, he'll fight it and make himself a victim if it was needed. No one important to him will get hurt by him, right?

 **A/N: So, I've been thinking about how the Monster Arm will come back and also read stuff like this, and wanted to do my own take on it. It got real dark in the beginning, but idk how it ended up a little sweet at the end. I didn't really have it too mapped out, so it may seem weird in the dialogue part. I'm very sorry about that. I am also sorry that this may seem a little OOC for Marco (I think I got Star's character okay, thought this is my first fanfic in SVFOE). I hope you all like this as much as I did while writing it! Please review, or make a comment on this and tell me your thoughts and my mistakes! I may or may not fix this up later on too!**

 **~aPieceOfPie**


	2. Chapter 1

**A/N: Hey, so I decided to try to make this a story but if all fails, I'll make this back into a OneShot called Nightmare. I hope you all like this! P.s to viewers before, the first chapter is going to be a prologue type of thing and if you have questions or if i messed something up, please comment or message me so I can fix this mistake! Please enjoy this chapter!**

It was a very dark night in Echo Creek. A new moon gave no light and most of the street lights near the school were close to dying making the lights flicker. So, seeing this, any sane person wouldn't be near this area at one in the morning. Sadly, he isn't sane.

It's been a full two months since his monster appeared. It has left a seemingly permanent, never ending flame of pain up his right arm. Messages had came through on his arm in odd dark markings up his arm, and had spelled things like _**Never going away, Give up,**_ or, _ **We need to FEED**_! It's creepy, but Marco knows that it's not saying to feed with his mouth, more like that _thing's_ mouth. That has been another reason he's been wearing long sleeves and just a weird one short sleeve and one long sleeve when it's too hot. But he can't hide it very longer.

As soon as month two came along, a letter came in for him. It said that in order to control this, he'd need this pill. Marco was too desperate to think about who sent it, that it could be poison, or how someone knew about his _condition._ Surprisingly, he had snuck out of the house at midnight when he was sure his family and Star were asleep. The man who he met that night was not someone he'd wanted to tangle with, but by then he had revealed that what the letter is about is true.

The cool night air blew the heat on his right arm off leaving goose bumps on his exposed skin. This had been the only time in the months that his arm has been exposed in such a public place. It felt nice. But the relaxing atmosphere was put to end as he felt the evil presence of his provider.

"My, you came early, are you that desperate?" The man's voice echoed in his ears with cruelty.

"Heh, I'm just trying to speed things up. You know, you aren't easy on my eyes," Marco replied with a smug smirk.

The man nodded and took off the hood of his trench coat, "Yes, well, you have no choice but to come back."

"Tsk," Marco glowered at the man, "Only because I'm forced."

The man said nothing and chose to open a briefcase containing the month supply bottle of pills that contain the beast in him. He lifted his middle fingerless hand to grab at the bottle and with it being touched, the bottle glowed a light hue of blue. It died down to show blue pills. It was never something Marco would be proud of ingesting.

"Thanks, Toffee," Marco said grimly. He took the pills and speed off to his home hoping to Mewni that Star isn't up.

Toffee stood where he had been left. He had a ominous smile on as he saw the boy stumble through the streets. Some day he hoped the boy figures out his place.

"Such a disappointment," He says with a frown before making his way through the rip in dimensions.


End file.
